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Barenboim, G., Martinez-Mirave, P., Ternes, C. A., & Tortola, M. (2020). Sterile neutrinos with altered dispersion relations revisited. J. High Energy Phys., 03(3), 070–18pp.
Abstract: In this paper we investigate neutrino oscillations with altered dispersion relations in the presence of sterile neutrinos. Modified dispersion relations represent an agnostic way to parameterize new physics. Models of this type have been suggested to explain global neutrino oscillation data, including deviations from the standard three-neutrino paradigm as observed by a few experiments. We show that, unfortunately, in this type of models new tensions arise turning them incompatible with global data.
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Barenboim, G., Martinez-Mirave, P., Ternes, C. A., & Tortola, M. (2023). Neutrino CPT violation in the solar sector. Phys. Rev. D, 108(3), 035039–10pp.
Abstract: In this paper, we place new bounds on CPT violation in the solar neutrino sector analyzing the results from solar experiments and KamLAND. We also discuss the sensitivity of the next-generation experiments DUNE and Hyper-Kamiokande, which will provide accurate measurements of the solar neutrino oscillation parameters. The joint analysis of both experiments will further improve the precision due to cancellations in the systematic uncertainties regarding the solar neutrino flux. In combination with the next-generation reactor experiment JUNO, the bound on CPT violation in the solar sector could be improved by 1 order of magnitude in comparison with current constraints. The distinguishability among CPT-violating neutrino oscillations and neutrino nonstandard interactions in the solar sector is also addressed.
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Barenboim, G., & Nierste, U. (2021). Modified majoron model for cosmological anomalies. Phys. Rev. D, 104(2), 023013–6pp.
Abstract: The vacuum expectation value v(s) of a Higgs triplet field Delta carrying two units of lepton number L induces neutrino masses alpha v(s). The neutral component of Delta gives rise to two Higgs particles, a pseudoscalar A and a scalar S. The most general renormalizable Higgs potential V for Delta and the Standard-Model Higgs doublet Phi does not permit the possibility that the mass of either A or S is small, of order v(s), while the other mass is heavy enough to forbid the decay Z -> AS to comply with LEP 1 data. We present a model with additional dimension-6 terms in V, in which this feature is absent and either A or S can be chosen light. Subsequently we propose the model as a remedy to cosmological anomalies, namely the tension between observed and predicted tensor-to-scalar mode ratios in the cosmic microwave background and the different values of the Hubble constant measured at different cosmological scales. Furthermore, if Delta dominantly couples to the third-generation doublet L-tau = (v(tau), tau), the deficit of v(tau) events at IceCube can be explained. The singly and doubly charged triplet Higgs bosons are lighter than 280 GeV and 400 GeV, respectively, and could be found at the LHC.
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Barenboim, G., & Park, W. I. (2019). Spontaneous baryogenesis in spiral inflation. Eur. Phys. J. C, 79(6), 456–11pp.
Abstract: We examined the possibility of spontaneous baryogenesis driven by the inflaton in the scenario of spiral inflation, and found the parametric dependence of the late-time baryon number asymmetry. As a result, it is shown that, depending on the effective coupling of baryon/lepton number violating operators, it is possible to obtain the right amount of asymmetry even in the presence of a matter-domination era as long as such era is relatively short. In a part of the parameter space, the required expansion rate during inflation is close to the current upper-bound, and hence can be probed in the near future experiments.
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Barenboim, G., Ternes, C. A., & Tortola, M. (2019). New physics vs new paradigms: distinguishing CPT violation from NSI. Eur. Phys. J. C, 79(5), 390–7pp.
Abstract: Our way of describing Nature is based on local relativistic quantum field theories, and then CPT symmetry, a natural consequence of Lorentz invariance, locality and hermiticity of the Hamiltonian, is one of the few if not the only prediction that all of them share. Therefore, testing CPT invariance does not test a particular model but the whole paradigm. Current and future long baseline experiments will assess the status of CPT in the neutrino sector at an unprecedented level and thus its distinction from similar experimental signatures arising from non-standard interactions is imperative. Whether the whole paradigm is at stake or just the standard model of neutrinos crucially depends on that.
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Barenboim, G., Ternes, C. A., & Tortola, M. (2020). CPT and CP, an entangled couple. J. High Energy Phys., 07(7), 155–12pp.
Abstract: Even though it is undoubtedly very appealing to interpret the latest T2K results as evidence of CP violation, this claim assumes CPT conservation in the neutrino sector to an extent that has not been tested yet. As we will show, T2K results are not robust against a CPT-violating explanation. On the contrary, a CPT-violating CP-conserving scenario is in perfect agreement with current neutrino oscillation data. Therefore, to elucidate whether T2K results imply CP or CPT violation is of utter importance. We show that, even after combining with data from NO nu A and from reactor experiments, no claims about CP violation can be made. Finally, we update the bounds on CPT violation in the neutrino sector.
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Barenboim, G., Turner, J., & Zhou, Y. L. (2021). Light neutrino masses from gravitational condensation: the Schwinger-Dyson approach. Eur. Phys. J. C, 81(6), 511–12pp.
Abstract: In this work we demonstrate that non-zero neutrino masses can be generated from gravitational interactions. We solve the Schwinger-Dyson equations to find a non-trivial vacuum thereby determining the neutrino condensate scale and the number of new particle degrees of freedom required for gravitationally induced dynamical chiral symmetry breaking. We show for minimal beyond the Standard Model particle content, the scale of the condensation occurs close to the Planck scale.
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Barreiros, D. M., Joaquim, F. R., Srivastava, R., & Valle, J. W. F. (2021). Minimal scoto-seesaw mechanism with spontaneous CP violation. J. High Energy Phys., 04(4), 249–21pp.
Abstract: We propose simple scoto-seesaw models to account for dark matter and neutrino masses with spontaneous CP violation. This is achieved with a single horizontal Z8 discrete symmetry, broken to a residual Z2 subgroup responsible for stabilizing dark matter. CP is broken spontaneously via the complex vacuum expectation value of a scalar singlet, inducing leptonic CP-violating effects. We find that the imposed Z8 symmetry pushes the values of the Dirac CP phase and the lightest neutrino mass to ranges already probed by ongoing experiments, so that normal-ordered neutrino masses can be cornered by cosmological observations and neutrinoless double beta decay experiments.
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Barrientos, L., Borja-Lloret, M., Casaña, J. V., Dendooven, P., Garcia Lopez, J. G., Hueso-Gonzalez, F., et al. (2024). Gamma-ray sources imaging and test-beam results with MACACO III Compton camera. Phys. Medica, 117, 103199–10pp.
Abstract: Hadron therapy is a radiotherapy modality which offers a precise energy deposition to the tumors and a dose reduction to healthy tissue as compared to conventional methods. However, methods for real-time monitoring are required to ensure that the radiation dose is deposited on the target. The IRIS group of IFIC-Valencia developed a Compton camera prototype for this purpose, intending to image the Prompt Gammas emitted by the tissue during irradiation. The system detectors are composed of Lanthanum (III) bromide scintillator crystals coupled to silicon photomultipliers. After an initial characterization in the laboratory, in order to assess the system capabilities for future experiments in proton therapy centers, different tests were carried out in two facilities: PARTREC (Groningen, The Netherlands) and the CNA cyclotron (Sevilla, Spain). Characterization studies performed at PARTREC indicated that the detectors linearity was improved with respect to the previous version and an energy resolution of 5.2 % FWHM at 511 keV was achieved. Moreover, the imaging capabilities of the system were evaluated with a line source of 68Ge and a point-like source of 241Am-9Be. Images at 4.439 MeV were obtained from irradiation of a graphite target with an 18 MeV proton beam at CNA, to perform a study of the system potential to detect shifts at different intensities. In this sense, the system was able to distinguish 1 mm variations in the target position at different beam current intensities for measurement times of 1800 and 600 s.
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Barrientos, L., Borja-Lloret, M., Casana, J. V., Hueso-Gonzalez, F., Ros, A., Roser, J., et al. (2023). System characterization and performance studies with MACACO III Compton camera. Radiat. Phys. Chem., 208, 110922–13pp.
Abstract: The IRIS group of IFIC-Valencia has developed a Compton camera prototype. The system detectors are made of Lanthanum (III) bromide scintillator crystals coupled to silicon photomultipliers. Two models of silicon photomultipliers arrays with different micro pixel pitch (25 and 50 μm) have been chosen as possible candidates to improve the response of the new system. Characterization studies with a 22Na point-like source have indicated that the 25 μm photodetector provided better performance in terms of energy resolution (5.2% FWHM at 511 keV) and angular resolution (6.9 degrees FWHM at 1275 keV), and more stability with temperature variations. In addition, MACACO III imaging capabilities have been assessed using a structure composed of thirty-seven 22Na point-like sources. Furthermore, in order to evaluate possible ways of improving the system performance, several studies have been carried out by means of simulations both in realistic and performance improved conditions. In this work, the system performance is evaluated for its future application in different areas.
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